The present invention relates to scroll type fluid machinery which can be suitably used, for example, for compressors for air or refrigerant, vacuum pumps, and the like.
Generally, as an example of scroll type fluid machinery, there is known a scroll type air compressor in which orbiting scrolls are respectively provided on axially opposite sides of a rotary shaft. By driving the rotary shaft, compression of air or the like is conducted at axially opposite sides of the shaft (see, for example, Japanese Patent Application Public Disclosure No. 2002-13492).
In a conventional air compressor of this type, first and second fixed scrolls are provided on axially opposite sides of a cylindrical casing. These fixed scrolls each comprise an end plate and a spiral wrap portion extending from a front surface of the end plate.
In the casing, there are provided a rotary shaft comprising a cylindrical rod and an electric motor for rotatably driving the rotary shaft. A connecting shaft is rotatably provided on an inner circumferential surface of the rotary shaft and extends through the rotary shaft. The center axis of the connecting shaft is radially offset from the center axis of the rotary shaft by a predetermined amount, and opposite ends of the connecting shaft project from axially opposite ends of the rotary shaft, to thereby form crank portions which are eccentric with respect to the rotary shaft.
These crank portions are connected to first and second orbiting scrolls, respectively. The orbiting scrolls each comprise an end plate and a spiral wrap portion extending from a front surface of the end plate. The wrap portion of each orbiting scroll overlaps the wrap portion of the first or second fixed scroll, to thereby define a plurality of compression chambers.
The end plate of each orbiting scroll is a plate-like member comprising two layers, with cooling fins and cooling air passages being formed therein. A metal plate or the like for connection with the connecting shaft is provided on a reverse side of the end plate.
To operate the air compressor, the rotary shaft is rotatably driven by means of the electric motor, and the first and second orbiting scrolls connected to opposite ends of the rotary shaft each perform an orbiting motion with respect to the fixed scrolls, to thereby compress air between the first fixed scroll and the first orbiting scroll, and between the second fixed scroll and the second orbiting scroll.
In this case, the respective end plates of the fixed scrolls and the orbiting scrolls are subject to high temperatures due to compression heat generated during a compression operation. Therefore, in the conventional air compressor, an electric cooling fan comprising an electric motor is provided in the vicinity of an outer periphery of each of the first and second fixed scrolls.
Then, during air compressor operation, the two electric fans are operated by externally supplying power to the motors so that one electric fan cools the reverse sides of the first fixed scroll and the first orbiting scroll, while the other fan cools the reverse sides of the second fixed scroll and the second orbiting scroll.
Thus, in the above-mentioned prior art, an electric fan is provided at an outer periphery of each of the first and second fixed scrolls. In this case, the two electric fans radially project from opposite ends of the air compressor. Therefore, a radial dimension of the compressor is large.
Further, due to attachment of two electric fans, a reduction in cost of the compressor is difficult. Due to operation of the electric fans, the compressor generates pronounced noise and a large amount of heat, and power consumption increases, resulting in poor product quality. In addition, in the compressor casing and the fixed scrolls, portions for attachment of the electric fans must be formed, and wiring for supply of power to the electric fans is required. Therefore, the structures of the casing and the fixed scrolls are complicated.
Further, in the conventional compressor, the end plate of the orbiting scroll is imparted with a two-layer structure so as to increase cooling performance, and an attachment plate to be connected to the connecting shaft is provided on the reverse side of the end plate. This complicates the structure of the orbiting scroll and requires cumbersome operations for machining and assembling the orbiting scroll, thus lowering productivity.